Map planimeter - photo

[Altair]

Map planimeter for measuring actual distances and areas on maps.

Fullsize image: https://diqn32j8nouaz.cloudfront.net...l_fullsize.jpg




Previously:

Early personal and in-car navigation - photos
ancient Chinese south-pointing chariot

[Frank S]

All they gave us to use was these

but military cartographers are among the best in the world when it comes to producing arcuate topographic maps from surveillance photos

[mklotz]

The device is called an opisometer.

https://en.wikipedia.org/wiki/Opisometer

[greyhoundollie]

I haven't seen one of those since 1970's in the Air Force. We had cartographers working with us with flight simulators. Making huge glass maps hand painted down to items the size of fence posts, the map covered sometimes 500 miles or more.

[baja]

Wow, I still have one of these in my desk!

[mklotz]

Map planimeter for measuring actual distances and areas on maps.

Green's theorem notwithstanding, it's not clear to me how one measures area with an opisometer, which measures linear dimensions. Typically area measurements are made with a device called a planimeter. Here's a good description of the device, including some pictures, history, use and its relation to Green's theorem

AMS :: Feature Column from the AMS

Of course, if you're out camping in the forest and have an urgent need to calculate an area, you can always use your pocket knife as a planimeter...

https://www.spaco.org/Blacksmithing/...Planimeter.htm

[Christophe Mineau]

Map planimeter for measuring actual distances and areas on maps.

Whoa , that's funny, the Map shown above, this is the place where I grew up, well, 20km above the town up right on the map.
This is what we call here a "curvimètre", not that uncommon, this is still sold and you can event get the digital high tech version :
https://www.amazon.fr/curvimetre/s?k=curvimetre